# 这是单行注释
'''
这是多行
注释
'''
# 三个双引号有两个作用，一是注释多行，二是定义多行字符串，所以在这里运行会有输出
"""
这是多行注释，用三个双引号
这是多行注释，用三个双引号 
这是多行注释，用三个双引号
"""

# 运行一下就好啦
set_1 = {"欢迎", "学习","Python"}
print(set_1.pop())   #为什么是Python？

#查看属性和方法
import decimal       #decimal包
from decimal import Decimal      #Decimal是decimal包里的对象

dir(decimal)    #查看decimal包中的属性和方法，包也是对象

a = decimal.getcontext()   #getcontext()显示Decimal对象的精度prec，rounding等等
print(a)

decimal.getcontext().prec = 4  #可以通过调整prec，将精度调到4位
c = Decimal(1) / Decimal(3)
print(c)

#可以用bool()将其他类型转换为bool型
print(bool(0.00),bool(10.31))    #bool()作用在基本类型变量，只要不是0，转换为bool类型后就是True
print(bool(()),bool('python'))   #bool()作用在容器类型变量，只要不是空，转换为bool类型后就是True

print(type(1))
print(isinstance(1,int))

print(int(520.52))   # int()转换为整型
print(float('520.52')) # float()转换为浮点型
print(str(10 + 10))   # str()转换为字符串

'''
和C++不同，/代表准确结果，//才是整除
'''
print(11/3)
print(11//3)

# 幂运算
print(2**3)

# 三元操作符
x, y = 4, 5
small = x if x < y else y
print(small)

print(-3 ** 2)   # -9
print(3 ** -2)   # 0.11111111111
print(-3 * 2 + 5 / -2 -4) # -12.5
print(3 < 4 and 4 < 5) # True

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

shoplist = ['apple','mango','carrot','banana']
print("This is printed without 'end' and 'sep'.")
for item in shoplist:
    print(item)

shoplist = ['apple','mango','carrot','banana']
print("This is printed with 'end='&''.")
for item in shoplist:
    print(item, end='&')

shoplist = ['apple','mango','carrot','banana']
print("This is printed with 'sep='&'.")
for item in shoplist:
    print(item, 'another string', sep='&')

n << m #计算n*(2^m)
n >> m #计算n(2^m)

#异或的性质：a^a=0,a^0=a
a ^= b  # a=a^b:
b ^= a  # b=b^a=b^(a^b)=a^(b^b)=a
a ^= b  # a=a^b=(a^b)^a=b^(a^a)=b

00 00 01 01 -> 5
&
11 11 10 11 -> -5
---
00 00 00 01 -> 1

00 00 11 10 -> 14
&
11 11 00 10 -> -14
---
00 00 00 10 -> 2

a | (1<<i)  -> 把 i 插入到集合中
a & ~(1<<i) -> 把 i 从集合中删除
a & (1<<i)  -> 判断 i 是否属于该集合（零不属于，非零属于）

a 补   -> ~a
a 交 b -> a & b
a 并 b -> a | b
a 差 b -> a & (~b)

print(bin(3))  # 0b11
print(bin(-3))  # -0b11

print(bin(-3 & 0xffffffff))  
# 0b11111111111111111111111111111101

print(bin(0xfffffffd))       
# 0b11111111111111111111111111111101

print(0xfffffffd)  # 4294967293

temp = input("猜一猜小姐姐想的是哪个数字？")
guess = int(temp) # input 函数将接收的任何数据类型都默认为 str。
if guess == 666:
    print("你太了解小姐姐的心思了！")
    print("哼，猜对也没有奖励！")
else:
    print("猜错了，小姐姐现在心里想的是666！")
print("游戏结束，不玩儿啦！")

temp = input('请输入成绩:')
source = int(temp)
if 100 >= source >= 90:
    print('A')
elif 90 > source >= 80:
    print('B')
elif 80 > source >= 60:
    print('C')
elif 60 > source >= 0:
    print('D')
else:
    print('输入错误！')

my_list = ['lsgogroup']
my_list.pop(0)
assert len(my_list) > 0

# AssertionError

string = 'abcd'
while string:
    print(string)
    string = string[1:]

# abcd
# bcd
# cd
# d

while 布尔表达式:
    代码块
else:
    代码块

count = 0
while count < 5:
    print("%d is  less than 5" % count)
    count = count + 1
else:
    print("%d is not less than 5" % count)
    
# 0 is  less than 5
# 1 is  less than 5
# 2 is  less than 5
# 3 is  less than 5
# 4 is  less than 5
# 5 is not less than 5

count = 0
while count < 5:
    print("%d is  less than 5" % count)
    count = 6
    break
else:
    print("%d is not less than 5" % count)

# 0 is  less than 5

member = ['张三', '李四', '刘德华', '刘六', '周润发']
for each in member:
    print(each)

# 张三
# 李四
# 刘德华
# 刘六
# 周润发

for i in range(len(member)):
    print(member[i])

# 张三
# 李四
# 刘德华
# 刘六
# 周润发

dic = {'a':1,'b':2,'c':3,'d':4}

for key,value in dic.items():
    print(key,value,sep=':',end=' ')

for key in dic.keys():
    print(key,end=' ')

for value in dic.values():
    print(value,end=' ')

for num in range(10,20):  #range(10,20)表示[10,20)
    for i in range(2,num):
        if num%i == 0:
            j = num / i
            print('%d 等于 %d * %d' % (num,i,j))
            break
    else:
        print(num,'是一个质数')

range([start,] stop[, step=1])

for i in range(9):
    print(i)

enumerate(sequence, [start=0])

seasons = ['Spring', 'Summer', 'Fall', 'Winter']
lst = list(enumerate(seasons))
print(lst)
lst = list(enumerate(seasons, start=1))
print(lst)

languages = ['Python','R','Matlab','C++']
for i, language in enumerate(languages, 2):
    print(i, 'I love', language)
print('Done!')

for i in range(10):
    if i % 2 != 0:
        print(i)
        continue
    i += 2
    print(i)

def a_func():

def a_func():
    pass

[expr for value in collection [if condition]]

a = [(i,j) for i in range(0,3) if i < 1 for j in range(0,3) if j > 1]
print(a)

[m+'_'+n for m in ['a','b'] for n in ['c','d']]

(expr for value in collection [if condition])

a = (x for x in range(10))
print(a)
print(tuple(a))

{key_expr: value_expr for value in collection[if condition]}

b = {i: i%2 == 0 for i in range(10) if i % 3 == 0}
print(b)

{expr for value in collection [if condition]}

c = {i for i in [1,2,3,4,5,5,6,4,3,2,1]}
print(c)

e = (i for i in range(10))
print(e)
'''
next(iterator[, default])
Return the next item from the iterator. 
If default is given and the iterator is exhausted, it is returned instead of raising StopIteration.
'''
print(next(e))
print(next(e))
for each in e:
    print(each, end=' ')

try:
    检测范围 
except Exception[as reason]:
    出现异常后的处理代码

dict1 = {'a': 1, 'b': 2, 'v': 22}
try:
    x = dict1['y']
except LookupError:
    print('查询错误')
except keyError:
    print('键错误')
else:
    print(x)

try:
    s = 1 + '1'
    int('abc')
    f = open('test.txt')
    print(f.read())
    f.close()
except (OSError, TypeError, ValueError) as error:
    print('出错了!\n原因是：' + str(error))

try:
    检测范围 
except Exception[as reason]:
    出现异常后的处理代码 
finally:
    无论如何都会被执行的代码

def divide(x, y):
    try:
        result = x / y
        print("result is", result)
    except ZeroDivisionError:
        print("division by zero!")
    finally:
        print("executing finally clause")
        
divide(2,1)
divide(2,0)

try:
    检测范围 
except(Exception1[, Exception2[,...ExceptionN]]]):
    发生以上多个异常中的一个，执行这块代码 
else:
    如果没有异常执行这块代码 

try:
    fh = open("testfile", "w")
    fh.write("这是一个测试文件，用于测试异常！！")
except IOError:
    print("Error: 没有找到文件或读取文件失败")
else:
    print("内容写入文件成功")
    fh.close()

try:
    raise NameError('HiThere')
except NameError:
    print('An exception flew by!')